What remained of the carnivore was discovered in Minnesota’s Tyson Spring Cave. Excavators had to create a tunnel to explore the Pleistocene deposit – the front entrance is underwater – and in doing so they found a partial skull of the “elk moose” Cervalces, a deer that sported an impressive set of antlers. Once inside, researchers found a partial skull, left shoulderblade, and right humerus of Homotherium scattered through the cave. These bones represent the first known record of the sabercat in the Great Lakes region.

The elk-moose Cervalces on display at the New Jersey State Museum. Photo by Brian Switek.

Genetic evidence supported what the skeletal anatomy indicated. Widga and coauthors were able to obtain a 311 base pair chunk of mitochondrial DNA from the Tyson’s Spring Cave bones, and this genetic fragment was a close match – differing in only two base pairs – from a previously-discovered Homotherium specimen.

In the larger scheme of cat evolution, Homotherium grouped most closely with the famous Smilodon, confirming that sabercats truly were an evolutionary lineage separate from other big cats. (This is why no one says “saber-toothed tiger” anymore. The sabercats split from a common ancestor with tigers and other big cats in the distant past.) This doesn’t mean that Homotherium and Smilodon were evolutionary siblings, though.

Based on anatomical evidence, paleontologists have separated Homotherium and Smilodon out into distinct sabercat lineages. Homotherium was a “scimitar-toothed cat” that belonged to the group Homotherini, while Smilodon was a “dirk-toothed cat” representing the Smilodontini (which sounds like a cocktail with bite). The separate lineages represented two different sabercat styles – Homotherium was a big leggier and had shorter, serrated canines, while Smilodon was a burlier predator with longer canines.  The reason the two came out as close relatives in the genetic analysis is that researchers have yet to extract and analyze DNA from other sabercats for comparison.

Of course, retrieving genetic clues from other sabercats will rely on the discovery of additional bones with preserved DNA. That might not be possible for the earliest sabercats, but Homotherium lived close enough to us in time that there’s hope of obtaining more scraps. The Tyson Spring Cave bones, in particular, are about 27,590-26,200 years old. Minnesota has changed quite a bit since then, though. According to Widga and coauthors, the cave was about 60 kilometers away from the nearest ice sheet in the middle of a nearly “treeless steppe-tundra environment” roamed by elk moose, mammoths, and the muskox-like Bootherium. And on that chilly open landscape, tracking the shaggy megamammals, was the last of America’s scimitar cats.

Reference:

Widga, C. Fulton, T., Martin, L., Shapiro, B. 2012. Homotherium serum and Cervalces from the Great Lakes Region, USA: geochronology, morphology and ancient DNA. BOREAS. 41: 546-556

Stretching over 26 feet long, and often said to weigh as much as five elephants, Paraceratherium has traditionally been heralded as the largest mammal ever to tromp over the Earth. The enormous rhino is practically required to make appearances in books, documentaries, and museum displays about fossil mammals. Yet, as paleontologist Donald Prothero demonstrates in his new book Rhinoceros Giants, old misconceptions about Paraceratherium cling to our imagination even as paleontologists are slowly piecing together a more complete picture of the superlative mammal.

For paleontology aficionados, the majesty of Paraceratherium is self-evident. The rhino was far larger than any alive today, and was an iconic member of mammal faunas that roamed Eurasia between about 35 and 20 million years ago. But Prothero spends no time trying to draw in those who are not already enamored with the titan. The first chapter of the relatively slim book – “Quicksand!” – jumps right into the romantic tales of fossil rhino discoveries in Mongolia during the American Museum of Natural History’s celebrated 1920s expeditions to the region. There is no introduction to what the giant rhinos were, or even why we should care at all that they existed.

For more than the first half of the book, in fact, Paraceratherium only appears as scattered fragments that puzzled and inspired successive generations of paleontologists. Prothero recounts the lives of fossil mammal researchers such as Walter Granger, Henry Guy Ellcock Pilgrim, Clive Forster Cooper, and Zhou Ming-Zhen, among others, in detail before diving into the geological particulars of where Paraceratherium bones are found and where the giant fit in the wider rhino family tree. While a giant rhino without a horn might look odd compared to living species, Prothero points out that Paraceratherium belonged to a major and totally-extinct group of rhinos, and that most fossil rhinos don’t show any evidence of horns at all. Modern rhinos might look prehistoric, but they’re actually quite different from their varied predecessors.

Through copious background details, Prothero celebrates great and lesser-known names in the history of paleontology, as well as geological and taxonomic nitty gritty. The problem is that the audience for all these particulars isn’t clear. In some sections, such as a lengthy review of taxonomic rules, Prothero lays out the basics of how species are named in textbook fashion for those unacquainted with such arcana. Yet an earlier chapter on the geology of Eurasia contains passages that only a trained researcher or especially avid avocational paleontologist would understand (“…the Hsanda Gol Formation consists of about 80 m of redbeds, floodplain mustones, and gray fluvial sands (Figs. 3.7, 3.8) that intertongue with the underlying Ergilin-Dzo where the Houldjin gravels are not present.”)

Frustratingly, Rhinoceros Giants often misses that sweet spot of readily-accessible science prose that Prothero has struck in other books such as Evolution: What the Fossils Say and Why it Matters. This problem is not unique to Rhinoceros Giants, but is rife within academic press books that are meant for popular audiences but are not composed or edited to meet the needs of such an audience. Rhinoceros Giants will primarily appeal to professional paleontologists and avocational fossil fans already familiar with many of the terms and concepts found within.

Yet, for fossil fans who are able to navigate the book, Rhinoceros Giants offers a valuable summary of what researchers presently understand about Paraceratherium. After laying out the historical and conceptual foundations of the book in the first half, Prothero begins to approach Paraceratherium proper. The complicated story of the mammal’s name is first on the agenda.

Paleontologists are generally agreed that Paraceratherium is the single valid name for all the huge fossil rhinos that roamed from eastern Europe through Mongolia during the Oligocene epoch. Yet, as a kid, I remember books and documentaries using names such as “Indricotherium” and “Baluchitherium” for the same animal. Prothero untangles the mess of names, created by incomplete knowledge of early finds and the idiosyncratic process of applying names to extinct animals. Paraceratherium has priority of place as a name, Prothero argues, and all the skeletons of the biggest rhinos so far known fall within the range of variation for this single genus.

With the beast’s rightful name established, Prothero proceeds to reconfigure the giant. Although, compared to other large mammals, Paraceratherium no longer seems quite so titanic. The rhino was tall and had a long, deep neck, but revised weight estimates have moved Paraceratherium away from oft-cited estimates of 30 tons towards a more modest 15-20 ton range. That’s still quite impressive, but comparable to estimates for large mammoths and other big fossil elephants. Paraceratherium just had a bit more vertical reach thanks to a long neck and, Prothero suggests, a prehensile lip. That’s a way of reaching high for food different from the elephantine method of extending a flexible trunk into the canopy.

Those two modes of browsing for food – having a long neck versus an extendable trunk on a head set lower to the ground – might have had something to do with why there are still elephants, but no enormous rhinos. Aside from reviewing the relatively small literature on the natural history of Paraceratherium, currently thought to have been a high browser that chewed soft tree leaves, Prothero also considers the various hypotheses for why the rhino’s lineage fizzled out. Most of these proposals – such as the wrongheaded notion that the rhinos suffered an “inadaptive” decline that drove them to extinction through a kind of evolutionary self-destruct – have themselves gone extinct. Instead, Prothero prefers the proposal of P.V. Putshkov and others that archaic elephants moved into Paraceratherium habitat and literally changed the landscape by stripping and pushing over the trees that the huge rhinos relied on. The arrival of a different kind of herbivore might have triggered ecological changes that drove the rhinos to extinction.

Paleontologists are as yet working with an outline of the evolution and extinction of Paraceratherium. Even the basic construction of the mammal’s skeleton is only partly known – reconstructions and restorations are based on parts from animals of different sizes and ages. Researchers are still striving to complete the skeletal structure of Paraceratherium. And despite being the most mega of the Cenozoic’s megafauna, we know considerably less about the natural history of Paraceratherium than many of the much older dinosaurs. Fossil mammals just don’t get the same research attention that Mesozoic celebrities do. Rhinoceros Giants is a handy synthesis of what paleontologists now know about the giant rhinos, but there are more mysteries about Paraceratherium than answers. Perhaps the book will inspire further work into Paraceratherium and other hefty mammals that are often obscured in the shadow of dinosaurs.

Top Image: Granger, W., Gregory, W. 1935. A revised restoration of the skeleton of Baluchitherium, gigantic fossil rhinoceros of Central Asia. American Museum Novitates. 787: 1-3

We’re 66 million years too late, at minimum, to directly observe non-avian dinosaurs. (And, much as I’m pained by saying so, cloning the long-lost creatures is impossible.) To investigate dinosaur lives, then, researchers often turn to living animals to examine the problems dinosaurs must have faced and possible solutions to common biological hurdles. How large dinosaurs coped with excess body heat is one of these puzzles.

Think of a relatively small dinosaur – let’s say the feathery, pigeon-sized Anchiornis – standing next to a fuzzy, 40-foot-long Tyrannosaurus. Compared to surface area, the larger dinosaur holds a greater volume. This means that the Tyrannosaurus will gain and lose body heat much more slowly than the little Anchiornis. On the positive side, this consequence of large size can help Tyrannosaurus maintain a high, constant body temperature in a phenomenon called gigantothermy. But the cost comes with exercise – a running Tyrannosaurus will quickly build up body heat that the dinosaur must somehow shed before hitting lethal internal temperatures. How did large dinosaurs manage to be the active animals we think they were without overheating?

Biologist Michael Rowe and coauthors suggest that living elephants might hold a few clues. While not at all closely related to dinosaurs, the big mammals still face some of the same problems related to body size and heat management. As detailed in their Journal of Experimental Biology study, Rowe and coauthors measured how two captive Asian elephants stored exercise-generated heat inside their bodies after walking outside under full sun in temperatures ranging from about 46 to 94 degrees Fahrenheit.

The amount of heat the elephants stored inside varied with the seasons. During November and February trials, the elephants were able to dump around 40% of the excess heat into the surrounding environment by changing bloodflow around the periphery of their bodies. But in the heat of the June trials, the skin of the elephants was too hot for this strategy to work. The elephants couldn’t shed any of the exercise-generated heat in the June trial. Since elephants can’t sweat, it’s no wonder that one of the test elephants – Panya – shuffled right into her pool to cool down for a few hours after some of the trials.

Based on the temperature fluctuations recorded in the captive animals, Rowe and coauthors calculated that an elephant could build up a lethal amount of internal heat if the behemoth walked continuously for four hours in an ambient temperature of about 88 degrees Fahrenheit. That’s problematic for animals that regularly travel long distances in the wild. To circumvent the heat problem, Rowe and collaborators suggest, elephants rely on behavioral solutions. Wild elephants can bathe and wallow in water sources along their travel routes to cool off, and walking at night would reduce heat stress for the huge mammals. There are other reasons for elephants to roam at night – avoiding humans, for one thing – but heat management is a possible benefit.

The bones of Edmontosaurus on display at the Natural History Museum of Los Angeles. Photo by Brian Switek.

Hefty dinosaurs, Rowe and coauthors hypothesize, might have employed similar strategies to keep their internal temperatures within safe limits. When the researchers applied the heat storage model they developed for elephants to the shovel-beaked hadrosaur Edmontosaurus – a roughly 40-foot-long, four-ton herbivore – they proposed that the dinosaur would have probably suffered a fatal amount of heat buildup after three and a half to four hours of continuous exercise. The variation in the estimate is based on different expectations about dinosaur physiology.

An endothermic Edmontosaurus – which would internally maintain a near-constant body temperature – would overheat in about three and a half hours, while an Edmontosaurus with a body temperature that varied according to the outside environment would only last about four hours. For such a big animal, there would hardly be any difference between the two strategies, and this undermines the idea – still favored by some dinosaur traditionalists – that big dinosaurs must have been ecothermic to prevent themselves from overheating. If the model proposed by Rowe and colleagues is correct, having an ectothermic metabolism doesn’t seem to provide very much benefit to big, active animals.

The geographic context of some Edmontosaurus also demonstrates that these dinosaurs were not just big lizards. As Rowe and coauthors point out, Edmontosaurus skeletons have been found within the Cretaceous Arctic Circle – an environment that would have been slightly warmer than today, but which still experienced snowfall and several months of total darkness every year. Rowe and colleagues state that these dinosaurs migrated out of the Arctic during these cold times, thus making the herbivores ancient analogs of far-traveling elephants, but evidence extracted from the inside the bones of Edmontosaurus indicates that these dinosaurs remained in the Arctic all year round. The dinosaurs were not restricted to the warm, lush habitats we so often imagine them in, but were capable of surviving in chillier habitats. If you were to travel back to the time of Arctic Edmontosaurus, you may very well have seen the dinosaurs trodding through the snow. To persist in such a place, the dinosaurs would have required a physiology more like that of modern birds and mammals than reptiles.

Edmontosaurus was not restricted to the Arctic. Fossils of this Late Cretaceous dinosaur are found from Alaska through Wyoming, and possibly even as far south as Texas. How Edmontosaurus and other dinosaurs in warmer climes dealt with heat is still an open question. Perhaps, like elephants, the dinosaurs got around the problem by roaming at night. Rowe and coauthors calculate that an adult Edmontosaurus would have accrued internal heat much more slowly in the cool of the evening, allowing the dinosaurs to move about four to five hours longer than during the day. And Edmontosaurus may not even represent the full range of options open to dinosaurs.

Birds are living dinosaurs. But many of the traits we think of as being peculiar to birds actually originated tens of millions of years ago, among the non-avian dinosaurs. The system of air sacs that extend from a bird’s respiratory system into bone – helping breathing efficiency, but also making the skeleton lighten without sacrificing strengths – appears to have evolved among Triassic dinosaurs. More specifically, air sacs seem to be a common feature of saurishcian dinosaurs – that big branch of the dinosaur family tree that contains the theropods, the sauropods, and their closest early kin. (Edmontosaurus, an ornithischian, was on the other side of the dinosaur split, and no ornithischian has yet been found with evidence of air sacs.) As P. Martin Sander and coauthors speculated in a major review of why sauropod dinosaurs such as Supersaurus got to be so huge, the air sac system might have provided a large surface area over which to shed heat during exhalation. The internal soft tissues of sauropods and theropods, at least, might have given them an effective way to rid themselves off heat generated from running around.

What Edmontosaurus could do, and what the animal actually did, are two different things. Testing hypotheses about how dinosaurs behaved is frustrated by the fact that most evidence of dinosaur behavior comes from trace fossils – tracks, body impressions, and similar petrified monuments. But in 2011 paleontologists Ryosuke Motani and Lars Schmitz hypothesized that the bony rings that supported dinosaur eyes might hint at what time of day particular dinosaurs might have beene active. A dinosaur with a large scleral ring and a big aperature in the middle would appear to have eyes suited to low-light conditions, for example, and so might have been more active at dusk or at night. Large hadrosaurs were among those that Motani and Schmitz studied. The researchers concluded that the dinosaurs Corythosaurus and Saurolophus fit expectations for “cathemeral” animals that would have been most active around dawn and dusk.

Yet the bony rings might not be as accurate an indicator of behavior as Motani and Schmitz proposed. In a response paper, Margaret Hall and colleagues pointed out that the scleral rings of birds and lizards active during the day are similar to nocturnal species. The connection between bone and behavior isn’t so clear cut. Motani and Schmitz defended their analysis in a further reply, but the debate remains open.

Given that there were undoubtedly thousands of non-avian dinosaur species between 245 and 66 million years ago, we can have every expectation that there were dinosaurs which were active at dawn, midday, dusk, and night. But establishing which dinosaurs were most active at what time is still quite difficult. We can easily envision a herd of Edmontosaurus walking through the Cretaceous night, and even calculate some of the benefits of such a strategy, but these visions still exist at the very edge of the clues we can draw from living animals and what remains of the great dinosaurs.

Top Image: Edmontosaurus regalis by John Conway.

References:

Chinsamy, A., Thomas, D., Tumarkin-Deratzian, A., Fiorillo, A. 2012. Hadrosaurs were perennial polar residents. The Anatomical Record. 295, 4: 610-614

Hall, M., Kirk, E., Kamilar, J., Carrano, M. 2011. Comment on “Nocturnality in dinosaurs inferred from scleral ring and orbit morphology.” Science. 334, 6063: 1641-1641

Rowe, M., Bakken, G., Ratliff, J., Langman, V. 2013. Heat storage in Asian elephants during submaximal exercise: behavioral regulation of thermoregulatory constrains on activity in endothermic gigantotherms. Journal of Experimental Biology. 216: 1774-1785

Sander, P., Christian, A., Clauss, M., Fechner, R., Gee, C., Griebeler, E. Gunga, H., Hummel, J., Mallison, H., Perry, S., Preuschoft, H., Rauhut, O., Remes, K., Tütken, T., Wings, O., Witzel, U. 2011. Biology of the sauropod dinosaurs: the evolution of gigantism. Biological Reviews. 86, 1: 117-155.

Schmitz, L., Motani, R. 2011. Nocturnality in dinosaurs inferred from scleral ring and orbit morphology. Science 322, 6030: 705-708

Schmitz, L., Motani, R. 2011. Response to comment on “Nocturnality in dinosaurs inferred from scleral ring and orbit morphology.” Science. 334, 6063: 1641-1641

The tottering, lizard-skinned Tyrannosaurus rex of my youth shuffled awkwardly after whatever was slow enough to catch, while the modern visions of the carnivore depict a fluffy tyrant with a spine held parallel to the ground and a respectable 10-15 mile per hour run. T. rex almost three decades after I first met the predator is a very different animal. But the great armor-plated dinosaur Stegosaurus hasn’t undergone the same degree of sweeping alterations. Not quite.

An oldschool Stegosaurus as illustrated by Charles R. Knight, featuring parallel plate rows and too many spikes. Image from Wikipedia.

When I visited Yale’s Peabody Museum of Natural History in New Haven, Connecticut last week, I didn’t immediately realize the ways in which the oldschool stegosaur was still off. Aside from too many tail spikes – eight in total, instead of four – the skeletal details looked more or less right. But then I noticed that the dinosaur’s tail was forced downward as much as the articulations allowed; the herbivore’s plates were arranged improperly in double, parallel rows; and the arms of Stegosaurus were splayed out to the side in the classic reptilian pose. And even though these particulars might seem minor, together they made the dinosaur seem just as awkward and dim-witted as I had often been told it must have been.

Stegosaurus isn’t going to stand like this forever. The Yale museum’s staff have big plans for their Stegosaurus, as well as their other dinosaurs. (I got a peek at the new fossil hall floor plans during my visit, and the new exhibits will be stunning.) But, for now, the Peabody’s Stegosaurus stands as a vestige to the slow, stupid, drab dinosaurs of my youth – an idiotic reptile that slouched through the Jurassic rather than proudly showing off its dermal decorations as the creature does in modern restorations.

Contrary to what I learned as a kid, Stegosaurus did not have a butt brain, nor did the dinosaur rely on the sun to warm up. And despite the variety of Stegosaurus renditions out there, lovely skeletons and evidence gleaned from them have shown that the famous dinosaur had plates arranged in a single alternating row and a thagomizer bearing four spikes. Stegosaurus was still among the oddest of all dinosaurs, but the image of the hefty herbivore as a stooped, moronic pile of ectothermic armor has been extinct for years now.

The constant wrangling of facts and theory have created an updated image of a more respectable and active dinosaur. Stegosaurus was not a prime example of extinction caused by investing too much energy in armor, as some 20th century paleontologists and pacifists, respectively, liked to claim. But the changes Stegosaurus has undergone since the days of the “Dinosaur Renaissance” seem relatively minor compared to earlier transfigurations.

The Yale paleontologist Othniel Charles Marsh named Stegosaurus in 1877. At the time, the infamous Bone Wars scientist had relatively little of the dinosaur’s skeleton to investigate and researchers had not even an inkling that anything like Stegosaurus (as we now know the dinosaur) ever existed. So we can’t really blame Marsh when he arranged the few known bones and plates into the form of a huge, turtle-like creature with a shell made of interlocking bits of triangular armor. (This is why the name Stegosaurus translates to “roofed lizard.”)

As he did with other dinosaurs – such as what became Triceratops, first described as a huge bison – Marsh changed his hypotheses based on new evidence. Additional Stegosaurus material showed him that his turtle-like interpretation was wrong for the plates, but the dinosaur’s spikes remained a puzzle. Marsh speculated that the weapons might have jutted from the dinosaur’s wrists as lances to jab and parry. This, too, turned out to be wrong when a quarry sketch showed the conical weapons in close association with the dinosaur’s tail. Marsh tweaked his speculations again, and finally, by about 1887, the standard form of Stegosaurus trod into view.

A modern vision of Stegosaurus, as restored by John Conway.

Stegosaurus will keep changing. How could it not? The dinosaur lived 150 million years ago, and we will never see a live one. Our understanding of what the dinosaur looked like and how the animal actually lived rely on the limits of what’s preserved in the rock and our ability to pull secrets from fossils, as well as whether or not we’re asking the right questions as we’re approaching the dinosaur’s remains. We can see Stegosaurus with greater clarity than ever before, yet many of the biological basics of the dinosaur – its physiology, how it ate, and what those funky plates were actually for, to name just a few – continue to confound and inspire. Decades down the line, should I be fortunate enough to still be alive, I may look back at this post, shake my head, and realize how little we yet knew about the late, great Stegosaurus.

The answer is simple enough. The “Okey Dokey Dino” has a frill and three horns – one over each eye, and one on the nose. That’s classic Triceratops. And, appropriately enough, the plush dinosaur seems to be a juvenile Triceratops.

In 2006, paleontologists Jack Horner and Mark Goodwin published a landmark paper on how dramatically the appearance of Triceratops changed as the dinosaur grew up. Indeed, contrary to the idea that baby dinosaurs were effectively tiny versions of adults that only got larger, Horner and Goodwin assembled a picture of dramatic change for Triceratops throughout the ceratopsid’s life.

As a baby, Triceratops was awkwardly adorable. The horns of the youngsters were small nubs, and their short frills were decorated by rounded ornaments called epiossifications. From there, the dinosaur took on a spikier appearance. Adolescent Triceratops had longer, backward-curving brow horns and sharper, arrow-shaped epiossifications set around an expanded frill. Then, as the herbivore approached adulthood, the brow horns remodeled to point forward, and those frill decorations flattened out. (Whether or not Triceratops continued to change after this point – taking on the form of the dinosaur traditionally called Torosaurus – remains a matter of investigation and debate.)

Within the bounds of Triceratops transformation, the fuzzy Wubbanub looks quite a bit like a juvenile. The toy’s horns are rounded little cones, and the brow stubs seem to curve ever-so-slightly backwards. So the Wubbanub might not be equivalent to the youngest Triceratops yet found, but the toy is pretty close to that infant – just old enough to see the subtle curve of horn that marks juvenile Triceratops.

Of course, this is assuming that the Wubbanub truly is a Triceratops. What if the toy is a unique dinosaurian genus, descended from the familiar Triceratops? (We’re 66 million years removed from the very last of the great horned dinosaurs, after all.) In that case, Wubbanub could be a case of neoteny – when on organism’s growth is slowed in such a way that adult animals retain juvenile traits. In fact, such a trend can be seen along the transition from non-avian dinosaurs to modern birds.

From Triceratops to the long-necked oddity Massospondylus and the ferocious Tyrannosaurus, many dinosaurs changed dramatically during their lives. But among birds – avian dinosaurs – babies look very much like adults and don’t undergo the same kinds of sweeping anatomical changes. As biologist Bhart-Anjan Bhullar and colleagues proposed in a paper published just last year, this may be because of a kind of neoteny that caused adult birds to retain traits seen in the juveniles of their non-avian dinosaur forerunners. Unfortunately, I don’t think I could actually publish a paper on “Neoteny in Wubbanubia” as Michael suggested, but the dinosaur pacifier inadvertently got one thing right – baby dinosaurs were adorable, big-eyed little critters that you didn’t have to be a mother Triceratops to love.

References:

Bhullar, B., Marugán-Lobón, J., Racimo, F., Bever, G., Rowe, T., Norell, M., & Abzhanov, A. (2012). Birds have paedomorphic dinosaur skulls. Nature. 487: 223-226

Horner, J., Goodwin, M. 2006. Major cranial changes during Triceratops ontogeny. Proceedings of the Royal Society B. 273, 1602: 2757-2761

Since the time the dinosaur was named in 2000, paleontologists have discovered multiple specimens of Microraptor in the 120 million year old lake deposits of China. Many of these are not only articulated, but fossilized to such a fine degree that the petrified remains of their feathers remain intact. This hi-def preservation also safeguarded tatters of Microraptor meals. One Microraptor individual, described two years ago, had feasted on an early bird shortly before perishing in a case of non-avian dinosaur eats avian dinosaur. But a Microraptor known as  QM V1002 enjoyed a different last meal.

Fossilized in the position of QM V1002′s stomach, paleontologist Lida Xing and colleagues explain in a new Evolution paper, are the scraps of bony fish. A small mass of fin rays, vertebrae, and other piscine tidbits are tucked between the dinosaur’s ribs, some of which had been etched by digestive fluids when the Microraptor was still alive. The question is whether this Microraptor actually caught fish or just happened along some convenient snacks thrown up onto the lakeshore.

The Microraptor known as QM V1002 fed on fish, just as the one designated IVPP V17972A ingested an archaic bird. But even such intimate associations as food in the guts of predators does not tell us how those carnivores actually obtained that ingesta.

In their paper on the bird-eating Microraptor, Jingmai O’Connor and colleagues proposed that the quad-winged dinosaur actively caught avian prey, thus supporting an arboreal lifestyle for the feathery deinonychosaur. But the Microraptor could have just as easily happened upon a dead bird and snaffled up the free meal. (The ground-dwelling, fuzzy dinosaur Sinocalliopteryx may have done the same.) Without a time machine, there’s no way to tease apart the evidence into a clear case of hunting or scavenging. We only have the mashed-up aftermath.

Microraptor in life – not unlike a toothy raven. Art by Jason Brougham/U. of Texas at Austin.

Such is frustratingly the case with the fish-eating dinosaur, too. While Xing and collaborators mention that fish flesh has a relatively short spoilage time, perhaps arguing against scavenging, there’s no way to distinguish between the two alternatives on the basis of the available evidence. All we know for sure is that Microraptor sometimes ate fish, just as the dinosaur consumed birds and (based on yet another specimen) small mammals. Microraptor was a predatory generalist, Xing and coauthors conclude, probably capable of snatching small prey while also enjoying the occasional opportunity  to horf down carrion.

Of course, technical papers must be conservative by nature. Saying that Microraptor hunted fish simply because one specimen was found with partially-digested fish flotsam inside, without considering other possible routes of ingestion, would be careless science. But dinosaurs are not just animals of technical journal arcana. Dinosaurs live where science and imagination meet, and, based on the spread of evidence, there is nothing illegitimate about picturing a Microraptor casting its wings over the water to create fish-friendly shade to attract swimming prey that could be then speared with a quick jab of a talon. Nor are visions of Microraptor gliding through Cretaceous forests to snatch early birds unreasonable or outlandish. These vignettes are prehistoric possibilities – what may have existed but remain just beyond the strict reach of direct scientific examination. The scattered data dots about the natural history of Microraptor may seem to be a sparse, limiting set of criteria, but, connected, they allow us to speculatively revive one of the most magnificent little carnivores of any era.

[Hat-tip to paleontologist Thomas Holtz, Jr. for pointing out the cat-deinonychosaur similarities that inspired this post's opening lines.

Top Image from the University of Texas at Austin.]

Reference:

Xing, L., Persons, W., Bell, P., Xu, X., Zhang, J., Miyashita, T., Wang, F., Currie, P. 2013. Piscivory in the feathered dinosaur Microraptor. Evolution. doi:10.1111/evo.12119

In terms of dinosaur superlatives, Dahalokely isn’t in the running for the classic titles of biggest, fiercest, or weirdest. Based upon the scattered vertebrae and rib pieces recovered from this animal, Farke and Sertich the bipedal dinosaur was modestly-sized at about eleven and a half feet long. And while no skull material has yet been found, Dahalokely probably chased after prey smaller than itself. The details of the Dahalokely bones indicate that this creature was an abelisauroid – a widespread group of carnivorous dinosaurs.

But the importance of Dahalokely isn’t so much in the dinosaur’s anatomy – of which we know relatively little as yet – but in the new geographical and evolutionary context the dinosaur provides.

As Farke recounts in his post on the new dinosaur, the discovery of Dahalokely was the result of a targeted effort to find dinosaurs on the island of Madagascar that are geologically older than those that have been discovered before. Previous efforts on the island have turned up a rich 70 million year old dinosaur fauna – including the big abelisaurid Majungasaurus, the armored sauropod Rapetosaurus, the snaggletoothed Masiakasaurus, and the small, bird-like Rahonavis – but more ancient dinosaurs are mostly known from hard-to-identify fragments. Fortunately, Sertich found the first bones of what would eventually be named Dahalokely in 2007, and helped pick up the rest of what remained in 2010. And as Farke and Sertich have now described, the bare bones pulled from that 94-89 million year old rock came from a critical time that set the stage of later dinosaur evolution on Madagascar and India.

Madagascar is a tatter of a landmass that has split and split again since the Cretaceous. About 130 million years ago, what is now mainland Africa began to split from adjoining landmasses, with what is now Madagascar and India still fused to prehistoric Antarctica. Thirty million years later, the Madagascar-India chunk broke from Antarctica, with Madagascar and India ultimately being ripped apart by about 88 million years ago.

Within the choreography of this continental dance, Dahalokely took the stage about 90 million years ago – while Madagascar and India were together, before the isolation of those pieces created living laboratories where dinosaur evolution diverged. And according to the analysis of Farke and Sertich, Dahalokely was more archaic than Majungasaurus, yet still had features shared among later abelisaurid dinosaurs on both Madagascar and India.

There’s no evidence that Dahalokely was directly ancestral to later dinosaurs on either landmass. And more than the current smattering of bones will be needed to further test and investigate exactly where the dinosaur fits among other abelisauroids. Nevertheless, Dahalokely might represent the general type of abelisauroid that existed on the joined Madagascar-India island before the two split.

If Farke and Sertich are right, Dahalokely – or something like it – set the stage for the later evolution of these blunt-nosed, stubby-armed predators as their traveling refuge split and the pieces continued to drift during the latter part of the Cretaceous. Dahalokely has become another reference point for how abelisauroid evolution unfolded over the course of millions of years, outlining how the “splendid isolation” of islands spurs evolution to bloom in fantastic ways.

For more on this dinosaur, and the journey from the field to publication, see Farke’s companion post on Dahalokely.

References:

Farke, A., Sertich, J. 2013. An Abelisauroid Theropod Dinosaur from the Turonian of Madagascar. PLoS ONE. 8, 4: e62047. doi:10.1371/journal.pone.0062047

I have a special fondness for paleopathologies. Dinosaur teeth and bones offer plenty of clues about how those animals lived, but isolated bones and even reconstructed skeletons can often be miscast as static monuments rather than representations of prehistoric vitality. But signs of injury and disease on a skeleton are immediately-recognizable indicators that those fossils represent what was once a living animal, and reflect specific events in the life of an individual. Among the latest of such clues to be described is a damaged tooth socket in the mouth of an Early Jurassic predatory dinosaur.

The injured dinosaur was a Sinosaurus triassicus – a crested, sharp-toothed dinosaur found in the roughly 200 million year old rock of China’s Yunnan Province. Sinosaurus looked something like Dilophosaurus from the Early Jurassic rock of the American southwest, so much so, in fact, that specimens of Sinosaurus were previously and erroneously thought to be a new species of Dilophosaurus from China. But taxonomic identity aside, paleontologist LiDa Xing and colleagues point out, what makes this particular Sinosaurus special is an entirely closed sixth tooth socket on the right side of the upper jaw. This is the first time this kind of pathology has been described in a theropod dinosaur.

By itself, the filled-in tooth socket might not seem especially strange. Carnivorous dinosaurs often damaged their teeth while chomping away on victims and carcasses. Cracked and broken teeth, sometimes found embedded in the bones of other dinosaurs, show that dental damage was a regular part of a predatory lifestyle. But dinosaurs continuously replaced their teeth throughout their lives. When a Sinosaurus lost a tooth, there was already another developing tooth slowly moving into place. So why would a dinosaur with a constantly-replenished tooth supply have a totally closed tooth socket?

Discerning exactly what caused dinosaur injuries is extremely difficult, if not often impossible. But based on the nature of the pathology, Xing and coauthors suspect that the Sinosaurus injury was caused by trauma rather than disease. The closed tooth socket lacks the messy, disorganized bone expected as the result of an infection, and instead hints that this dinosaur damaged the tooth so dramatically that even the replacement teeth in the jaw were wounded. Perhaps Sinosaurus clamped onto a Lufengosaurus just a tad too hard, or otherwise miscalculated during a bite. Whatever the case, that tooth position was so wrecked that the dinosaur’s jaw shut down the dental conveyor belt and closed up the socket.

But the Sinosaurus was tough. The dinosaur didn’t break a tooth and quickly perish. The fact that the tooth socket was fully closed indicates that the Sinosaurus lived for months or years after the injury, taking down prey with one less tooth in its arsenal.

Reference:

Xing, L., Bell, P., Rothschild, B., Ran, H., Zhang, J., Dong, Z., Wei, Z., Currie, P. 2013. Tooth loss and alveolar remodeling in Sinosaurus triassicus (Dinosauria: Theropoda) from the Lower Jurassic strata of the Lufeng Basin, China. Chinese Science Bulletin. DOI: 10.1007/s11434-013-5765-7

Sometime between 1901 and 1906, the Natural History Museum in Vienna, Austria acquired a trio of turtle specimens from the Zoological Museum Hamburg. According to the labels, the reptiles had been collected by the German naturalist August Brauer a decade before, when Brauer sampled critters from the island of Mahé – part of the Seychelles island chain, situated nearly halfway between India and Madagascar. Strangely, though, the turtles closely resembled a species found hundreds of miles away on mainland Africa.

A map showing the range of Pelusios castaneus (blue) and the supposed island species P. seychellensis (red). From Stuckas et al., 2013.

When the Viennese zoologist Friedrich Siebenrock had a look at the preserved reptiles in 1906, he was struck by how closely Brauer’s turtles resembled a turtle now known as Pelusios castaneus - a turtle found over a wide swath of western Africa. If the distance between the mainland and island turtles were not so great, Siebenrock commented in his description of the Mahé turtles, he’d be tempted to call them the same species. But there was no way the little turtles could have crawled all the way across Africa, nor somehow dispersed from habitat to habitat around the edge of the continent. The distance deemed that the two had to be different species.

Not everyone agreed with Siebenrock’s conclusion. For years afterward, different researchers often lumped Brauer’s turtles into the west African species or another island species on the basis of anatomy. That is, until 1983 when herpetologist R. Bour proposed that Brauer’s old specimens truly did represent a distinct species. Bour called the turtles Pelusios seychellensis, and it seemed that Brauer had collected some of the last ones. Several searches after 1983 tried, and failed, to find the turtles. In the span of a century, it seemed, Pelusios seychellensis had gone extinct – perhaps the only time on record that humans totally exterminated a species of freshwater turtle.

But Siebenrock’s hunch about the connection between the island and mainland turtles was more right than he knew. When Stuckas, Gemel, and Fritz sampled mitochondrial DNA from the museum specimen that bears the name Pelusios seychellensis and compared those genetic clues to those of other turtles, they found that the museum specimens fell within the range of variation for west African Pelusios castaneus individuals. The unique island species never actually existed. Somehow, researchers had misidentified Brauer’s specimens. But how could west African turtles have found their way to Mahé? According to Stuckas and colleagues, they didn’t.

There’s no evidence that Brauer’s turtles hauled themselves clear across Africa. Nor is there any indication that humans brought them there at some point in the past. All this confusion might simply be the result of poor labeling and miscommunication.

Brauer took the trip during which he was supposed to have collected the turtles between May 1895 to January 1896. But he didn’t immediately give his finds to a museum. Specimens from his private collection didn’t get transferred to the Zoological Museum Hamburg until five years after the Seychelles trip, and those turtles soon went on to Vienna’s Natural History Museum. Somewhere in all that shuffling, the west African turtles might have been lumped in with the Seychelles reptiles or otherwise confused. Whatever happened, though, a prominent clue indicates that the turtles were not collected from the wild. One, and possibly two, of the turtles have a perforation through their shells identical to the sort that turtle purveyors have traditionally used to tie turtles together until they are sold for food. Wherever Brauer got the turtles from, he seems to have purchased them.

This isn’t the first time bad bookkeeping has led zoologists to erroneously erect new species. Stuckas and coauthors point out two other instances – a mislabeled American snapping turtle was confused for what was thought to be a new species from New Guinea’s Fly River, and a supposed new tortoise found in Vietnam turned out to be “an escaped pet tortoise from Madagascar.” This is why well-kept locality data and responsible curation practices are essential. We need to know when, where, and how a specimen was collected to understand what we’re studying. (Paleontologists also know this well.) And that context is not only essential for exploring the diversity of life, but also conservation. In our efforts to assist imperiled species, we need to know whether or not we’re looking at something unique and critically endangered, a wayward member of a more common species, or whatever other alternative may be the case. Understanding even such a basic facet of ecology as the identity of a species requires a great deal of attention and care.

Reference:

Stuckas, H., Gemel, R., Fritz, U. 2013 One extinct turtle species less: Pelusios seychellensis is not extinct, it never existed. PLoS ONE 8, 4: e57116. doi:10.1371/journal.pone.0057116

Visiting “Brontosaurus” at the American Museum of Natural History was a critical moment that crystallized this prehistoric passion of mine, and seeing Jurassic Park for the first time gave life to old bones so magnificently that when I left the theater I knew I just had to find some way to chase down dinosaurs where they rested in rock. There was nothing greater for a 10 year old dinosaur nerd than to see Tyrannosaurus and Triceratops seemingly alive again, and I hoped that I might get a chance to dig after bones just like the film’s fictional paleontologists did.

All of which is to say that I’m thrilled Jurassic Park is back in theaters to celebrate the classic film’s 20th anniversary. The movie is still the best dinosaur film ever made, and, for better or worse, established THE image of what dinosaurs were like for an entire generation. And to celebrate the cinematic return of the most realistic dinosaurs ever to stomp across the screen, today I’m proud to present five different articles that encapsulate the joys and frustrations of Jurassic Park.

Part of the reason why Jurassic Park was so special is because the film combined science, special effects, and an imaginative tale in a way that is rarely seen among blockbusters. We’re never going to be able to clone dinosaurs, as I explain over at Mental Floss, but Michael Crichton came up with an ingenious and plausible-sounding way of reinventing dinosaurs for the story on which the film was based. And with that story in place, special effects masters were able to combine puppets with computer-generated imagery to create the closest thing to living dinosaurs. As I explain in a countdown of the best and worst cinema dinosaurs for Tor.com, Jurassic Park‘s Tyrannosaurus rex is the greatest Mesozoic celebrity ever resurrected on screen. Even as researchers are discovering more about how T. rex actually lived, which I review in a National Geographic item, paleontologists think that the movie’s tyrant still holds up pretty well by today’s scientific standards.

That doesn’t mean that Jurassic Park is a flawless depiction of dinosaurs or paleontology. When science and special effects come together, the movie is wonderful, but there are some real *headdesk* moments throughout. The part that always makes paleontologists I know snort and chuckle in disbelief is the early camp scene, where excavating a dinosaur is shown as little more than dusting off rock until a lovely articulated skeleton comes into view. As I describe over at Slate, this scene is also the one instance I know of where someone is caught picking a dinosaur’s nose in a major motion picture.

And as much as I cherish Jurassic Park, the film’s legacy is a mixed one. I explore my conflicted feelings about this in a post at io9. The first film was actually quite progressive about insisting that birds are dinosaurs, as well as using then up-to-date science to revive dinosaurs (even if the filmmakers didn’t always pay heed to paleontological particulars). This sparked a new wave of dinomania that helped inspire the generation of paleontologists who are overjoyed that the movie is back. All day, I’ve seen paleontologist friends and colleagues say how excited they are to watch Jurassic Park in theaters again.

But Jurassic Park is also a time capsule of dinosaurs circa 1993 which misguided, diehard fans regard as immutable canon. The film’s dinosaurs have become so entrenched in the public imagination that there is much weeping, wailing, and gnashing of teeth at the suggestion that maybe the fourth film in the series – set to debut sometime next year – should again mix the best of science and imagination by featuring feathery, bird-like dinosaurs.

Fictional paleontologist Alan Grant had a relentless enthusiasm for bird-like dinosaurs in the first film, but now it seems that devotees of the series, including Jurassic Park 4‘s director Colin Tevorrow, are more concerned about maintaining loyalty to outdated imagery than doing justice to dinosaurs. That’s a shame, but underscores just how powerful Jurassic Park was in shaping our perception of what dinosaurs were. Whether in the continuing Jurassic Park saga, or some other film, I hope filmmakers take the original installment’s lesson and combine true tales from the fossil record with the ferocious, amazing creatures that stalk our imaginations.

Bonus Reel:

A few weeks ago, I recorded a lighthearted review of Jurassic Park with the incomparable Lali DeRosier and Danielle Lee. I had a blast, especially considering what a dinosaur mix-and-matched from various strands of recovered DNA might look like. Poor “Puzzles.”

And if you haven’t had enough of my paleo pedantry yet, check out this vintage post from Dinosaur Tracking about why Jurassic Park‘s raptors don’t actually look like the real Velociraptor.  Even though the movie made “raptor” a household word, the fact is that the film’s most rapacious killer is actually another dinosaur named Deinonychus who was renamed for the movies.